Early in the day prepare sauce: Drain tomatoes and place in a medium bowl with olive oil, garlic, basil, parsley, salt, and oregano. Cover and let stand at room temperature.

Cut spaghetti squash in half, remove seeds, and drizzle with olive oil. Bake at 400 degrees for 40 to 45 minutes, or until tender when pierced with a fork. Let cool and use a fork to scrape spaghetti strands of squash from shell into a large bowl. Cover and set aside.

Steam broccoli, zucchini, and summer squash until each is fork tender; rinse in cold water to prevent further cooking and keep fresh color. Heat olive oil in large skillet and saute scallions until soft. Add steamed vegetables and heat thoroughly. Toss spaghetti squash with hot vegetables and tomato sauce. Sprinkle with Parmesan cheese and season with pepper. Serve warm or at room temperature.